The present invention relates to a new and improved construction of an electrostatic spray gun, sometimes also referred to in the art as an electrostatic powder coating gun.
The spray gun of the invention is of the type comprising an installed high-voltage generator and an installed switch means for turning-on and turning-off the high-voltage generator at its low-voltage side. Further, there is provided a flow channel for an atomizing gas, the flow channel being connected to a pressure line and within such flow channel there is arranged a manually-actuatable closure valve.
Such type spray gun is known to the art, for instance from Swiss Pat. No. 496,481. One of the advantages of such spray gun resides in the fact that by virtue of incorporating the high-voltage generator within the spray gun itself, it is possible to supply the high-voltage generator with electric energy at a low voltage or potential, i.e., by means of conductors or lines without the need for complicated insulation. With the heretofore known spray guns the switch or switch means constitutes a microswitch which can be mechanically actuated by a gun trigger bracket. As a result, the high-voltage generator remains turned-on as long as the trigger bracket is pressed, even then when a disturbance arises in the flow of the atomizing gas, whether such be because of failure of the pressure source delivering the atomizing gas or clogging of the atomizing nozzle.
This is associated with certain drawbacks, for instance also for the operation of the spray gun, since in the presence of a disturbed gas flow there can form weakly conductive bridges at the region of the atomizing or spray nozzle, i.e., at that location where there are arranged the charging electrodes. These weakly conducting bridges impair the charging and transport field for the atomized particles of the coating material, also after there has been eliminated the disturbance in the flow of the atomizing gas.